Water pollution is one of the global challenges that society must address in the 21st century aiming to improve water quality and reduce human and ecosystem health impacts. Industrialization, climate change, and expansion of urban areas produce a variety of water pollutants. In this work, we discuss some of the most recent and relevant findings related to the release of heavy metals, the possible risks for the environment and human health, the materials and technologies available for their removal. Anthropogenic activities are identified as the main source of the increasing amounts of heavy metals found in aquatic environments. Some of the health hazards derived from repeated exposure to traces of heavy metals, including lead, cadmium, mercury, and arsenic, are outlined. We also give some perspectives about several techniques used to detect heavy metals, as well as about the factors that could affect the contaminant removal. The advantages and drawbacks of conventional and non-conventional heavy metal removal methods are critically discussed, given particular attention to those related to adsorption, nanostructured materials and plant-mediated remediation. Some of the commercial products currently used to eliminate heavy metals from water are also listed. Finally, we point out some the requirements and opportunities linked to developing efficient methods for heavy metal removal, such as the ones that exploit nanotechnologies.

Heavy metal water pollution: A fresh look about hazards, novel and conventional remediation methods

Chromium is a potentially toxic and carcinogenic metal originating from natural processes and anthropogenic activities such as the iron steel, electroplating and leather industries. Therefore, chromium should be removed from wastewater to avoid environmental pollution and to recycle chromium in the context of the future circular economy. Here we briefly review aqueous Cr species, their toxicity and methods to remove Cr such as membrane filtration, chemical precipitation, ion exchange, adsorption electrocoagulation, electrochemical reduction, electrodialysis, electrodeionization, photocatalysis and nanotechnology.

Removal of chromium from wastewater by membrane filtration, chemical precipitation, ion exchange, adsorption electrocoagulation, electrochemical reduction, electrodialysis, electrodeionization, photocatalysis and nanotechnology: a review

Synthesis of carnation flower-like Bi2O2CO3 photocatalyst and its promising application for photoreduction of Cr(VI)

Biological remediation technologies for dyes and heavy metals in wastewater treatment: New insight.

Biological remediation technologies for dyes and heavy metals in wastewater treatment: New insight

Lead sulfate was chose to precipitate chromium (VI) based on the difference of the solubility between lead sulfate and lead chromate. The effects of parameters on the precipitation efficiency of chromium including reaction temperature, reaction time, and initial pH of solution and dosage of lead sulfate were investigated. Results showed that the initial pH of solution and dosage of lead sulfate had big influence while reaction time and reaction temperature had little. The concentration of chromium (VI) could reduce from 0.2 mol/L to 0.0015 mmol/L (0.08 mg/L) at pH value of 13.90 and the dosage of lead sulfate as n (PbSO4)/n (K2CrO4) = 4. The XRD result of precipitation was consistent with the result predicted by Visual MINTEQ software and the precipitation was composed of PbCrO4, PbSO4 and other oxides containing lead. Otherwise, XRF and ICP were used to analyze the residual lead (II) in the filtrate and results indicated that the concentration of Pb (II) in the filtrate was acceptable.

High-efficient recovery of chromium (VI) with lead sulfate

Acid leaching technology was introduced to leach out vanadium from calcification roasting converter vanadium slag. The effects of solid-to-liquid ratio, concentration of acid solution, reaction temperature, reaction time and particle size on leaching efficiency of vanadium were examined. A new defined parameter, encapsulation efficiency, was applied to describe the leachate loss in the filtration process. Results showed that the leaching efficiency of vanadium and encapsulation efficiency had opposite change trends. Under the optimal conditions (solid-to-liquid ratio of 50 g slag/200 mL acid solution, concentration of 0.25 mol/L H2SO4, reaction temperature of 323 K, reaction time of 60 min, particle size under 75 μm and stirring rate of 500 rpm), the leaching efficiency and encapsulation were 91% and 6%, respectively. The calcium sulphate formed during the leaching process would absorb on the surface of slag and block the pore channel between the particles, and it had negative effect on filtration process. The shrinking core model expressed by [(1-η)−1/3−1] +1/3ln (1-η) = kt was used to describe the leaching kinetics of vanadium in sulphur acid solutions. And the apparent activation energy of vanadium extraction was determined to be 12.45 kJ/mol, which indicated that the leaching process was controlled mainly diffusion of solution through surface layer.

Leaching kinetics of vanadium from calcification roasting converter vanadium slag in acidic medium

This paper focused on the treatment of vanadium–chromium reducing residue with a two-step alkaline leaching process: electro-oxidation leaching of vanadium and H2O2 as well as oxidation leaching of...

Recovery and Separation of Vanadium and Chromium by Two-Step Alkaline Leaching Enhanced with an Electric Field and H2O2.

Response surface methodology was applied to optimize the processing parameters (dosage of NaOH, dosage of H2O2, reaction temperature, liquid-to-solid ratio, stirring rate, and reaction time) that affected the leaching process of vanadium and chromium. The results indicated that the leaching process of vanadium was significantly affected by the dosage of NaOH and dosage of H2O2 used in the experiments, whereas the processing parameters affected the leaching efficiency of chromium in the following order: dosage of H2O2 (F) > reaction temperature (C) > dosage of NaOH (A) > reaction time (B) > stirring rate (D) > liquid-to-solid ratio (E). Almost 98.60% of vanadium and 79.82% of chromium were leached out during the leaching process.

https://pubs.acs.org/doi/pdf/10.1021/acsomega.8b02708

Jing Guo

Papers

Removal of chromium from wastewater by membrane filtration, chemical precipitation, ion exchange, adsorption electrocoagulation, electrochemical reduction, electrodialysis, electrodeionization, photocatalysis and nanotechnology: a review

High-efficient recovery of chromium (VI) with lead sulfate

Leaching kinetics of vanadium from calcification roasting converter vanadium slag in acidic medium

Recovery and Separation of Vanadium and Chromium by Two-Step Alkaline Leaching Enhanced with an Electric Field and H2O2.

Highly Efficient Recovery of Vanadium and Chromium: Optimized by Response Surface Methodology.